Regulated Exciton Dynamics and Optical Properties of Single Perovskite CsPbBr3 Quantum Dots by Diluting Surface Ligands

The surface state of all-inorganic cesium lead halide (CsPbX3) perovskite quantum dots (QDs) is a crucial factor for the performance of CsPbX3 QD-based optoelectronic devices. In this research, we demonstrate a rational and efficient approach for regulating the surface state of CsPbBr3 QDs by diluting surface ligands. With a systematic investigation of the optical properties of CsPbBr3 QDs from ensemble to a single particle by decreasing the surface ligands, we proposed that two competitive exciton decay pathways of single exciton deactivation, short-lived band-edge emission (∼3 ns) and long-lived surface trap-state emission (∼6–12 ns), are closely related to the emission behavior and optical properties of CsPbBr3 QDs. These findings are of significance in understanding the nature of surface ligand density, trap states, and their roles in the photoluminescence quantum yield and in improving the optical property, efficiency, and stability of CsPbX3 QD-based devices.